Note: * When the load current is higher than 10A, a heat sink must be added to the SSR or the SSR should be mounted on a metal base plate with heat dissipation effect, and apply the thermal grease between them. When the load current is higher than is 40A or more, fan forced cooling or water cooling is needed.* Heat sink is Not included.

Solid State Relay Dimensions

3 Phase SSR Wiring Diagram

Tips: The advantages of solid state relay over AC contactors

In the first place, solid state relay have a long life and high reliability. solid state relays do not have mechanical components, and use solid state devices to complete the contact function. Because there is no movement of those components, they can work in an environment full of high impact and vibration. Inherent characteristics of SSRs’ components determine their long life and high reliability. However, poor contact failure and then burned contactors may be caused by coils which are used by AC contactors to control magnetic drawing for the purpose of contacts’ connection or disconnection.

Solid state relays have good sensitivity, low control power and good electromagnetic compatibility. The SSR has a wide input voltage range and low drive power, which makes it compatible with most logic integrated circuits without a buffer or driver.

Solid state relays have fast conversion. Because solid state relays adopt solid state components, their switching speed can be from a few milliseconds to a few microseconds, and the conversion speed is very fast; and AC contactors’ drawing is controlled through coils, so the conversion speed is a few tenths of seconds, slow relative to solid state relays.

Solid state relays have small electromagnetic interference. Because there is no input coil in SSRs, no contact striking and bound, electromagnetic interference is reduced. Most AC-output solid state relays are zero-voltage switches that turn on at zero voltage and turn off at zero current, which reduces sudden interruption of the current waveform and thus reduce switching transient effects. However, the contactor’s electromagnetic interference is larger.

Solid state relays are small while contactors are large in volume. It is not convenient for contactors to be installed in some relatively narrow space while SSRs may come in convenient. Nevertheless, solid state relays do not have that large current generally, but contactors do.

Solid state relays can have various voltage conversions, such as AC to AC, AC to DC, DC to DC, etc. Contactors can not be so flexible.